Organ transplantations have opened a new field in medicine and particularly in pediatrics. The kidney was the first organ to be regularly transplanted and there are now more than 2000 children who have received a kidney graft. Cadaver kidneys or living-related donor (LRD) kidneys can be used since an adult kidney may be grafted in a young child. Cadaver graft survival exceeds 85% at 1 year in recent single centre reports and patient survival is above 95%, the results being even better with LRD. Some complications may be observed in the long term, such as bone osteonecrosis, hypertension or infections. Rehabilitation is generally remarkable and growth which remained abnormal in 1/3 of cases under conventional treatment seems to improve markedly with cyclosporin. In the future, the development of kidney transplantation could lead hopefully to a drastic decrease in the number of children on dialysis. Liver transplantation is now performed in children with biliary atresia and metabolic diseases. There is no age limit for grafting a liver, the only problem being to find a pediatric cadaver donor of similar size. It is also possible to use an adult liver after hepatectomy. There were 170 liver grafts recorded in children in Europe in December 1986, and the long-term survival thanks to cyclosporin is exceeding 80% in some units. Thanks to cyclosporin, programs of cardiac transplantation for children are rapidly developing. The main indications are gross-congenital cardiac malformations or severe functional abnormality not compatible with life. Newborns have been grafted with success. The only problem is also to find a suitable pediatric donor.(ABSTRACT TRUNCATED AT 250 WORDS)